The present invention relates generally to heating, ventilation and air conditioning (HVAC) systems and, more particularly, to a system and method for controlling the output flow of parallel connected blowers to maximize efficiency thereof.
Heating, ventilation, and air conditioning (HVAC) is the technology of indoor and automotive environmental comfort. In HVAC systems, fans and blowers are used to move air and are an integral part of the air handling systems that bring or draw fresh air into buildings. HVAC fans and blowers can be mounted to an exterior wall (ventilation unit) or above the ceiling (plenum fan), or used as part of a ducted system (duct fan). The fan spins or the blower turns by means of an electric motor, thus creating unidirectional air flow. Types of HVAC fans and blowers include vents or ventilation fans, plenum fans, duct fans, duct blowers, roof fans, exhaust fans, inline fans, tube axial fans, vane axial fans, and centrifugal blowers.
According to various system designs, the HVAC fans/blowers can be connected in series or parallel. There are many applications in HVAC design where it is desirable or even necessary to run the fans/blowers in parallel, such as based on space constraints or a desire to provide greater flow, or to provide diversity or standby capability (i.e., backup fan/blower). In some cases, the fans/blowers are identical and in others they may not be identical—primarily because the second fan/blower was added later to increase capacity. The fans/blowers are normally connected to a plenum, with the flow from each fan/blower adding up to meet a specified flow requirement.
In operating the fans/blowers, there are various combinations of speed at which the two fans/blowers can be operated to meet the desired total flow. The combination of speed at which the two fans/blowers are operated dictates, in large part, the overall power consumed in driving the fans/blowers and the efficiency at which the HVAC system is run. As ventilation fans/blowers are, energy-demanding equipment that stand for a significant share of a HVAC system's total energy consumption, the combination of speed at which the two fans/blowers are operated thus is an important factor in improving energy efficiency during system operation and in reducing the total power consumed by the system.
It would therefore be desirable to provide a system and method that enables controlling the output flow of parallel connected fans/blowers to maximize efficiency thereof.